If “Your Highness” teaches us anything, it’s the value of a decent screenplay. Reasonably well acted and technically impressive, the picture’s only major failing is in its writing, but that’s enough to completely sink the flimsy enterprise. Under the guidance of David Gordon Green “Your Highness” is aesthetically pleasing, but the film never manages to find a rewarding comedic groove, instead opting for obvious jokes and puerile references to male reproductive organs. I desperately wanted to like this slice of medieval tomfoolery, but instead I was left shocked by its unrelenting witlessness.

The remote Kingdom of Mourne has two Princes, brave and handsome Fabious (James Franco) and his selfish and ignorant brother Thadeous (Danny McBride). On the day of his wedding, Fabious has his bride Belladonna (Zooey Deschanel) stolen away from him, the thief revealing himself to be the wicked wizard Leezar (Justin Theroux). Leezar needs Belladonna in order to fulfill a contemptuous prophecy, requiring the young maiden’s virginity for his own ends. Fabious sets out to save her, dragging a reluctant and oafish Thadeous along for the ride. They swiftly meet up with a hardened warrior named Isabel (Natalie Portman), the unlikely trio enduring betrayal, danger and insurmountable odds in order to try and rescue Belladonna.

“Your Highness” is a good looking film, shot attractively in the hilly and lush countryside of Northern Ireland. Green endows the picture with a necessary sense of scale, concocting a wide and at times immersive world for his foolish heroes to inhabit. At the very least the startling cinematography and natural beauty of the film’s shooting locations will act as a solid travel brochure, some of the scenery in “Your Highness” surprisingly reminiscent of the gorgeous New Zealand landscapes found in Peter Jackson’s celebrated “The Lord of the Rings” trilogy.

Danny McBride assumes leading man status for the first time in a major studio feature with “Your Highness”, turning in a sufficient albeit fairly standard village idiot performance. However McBride also has the distinct dishonor of having contributed to the film’s wretched screenplay, an inanely plotted and humorless example of comedic craft. I have no problem with vulgarity, but “Your Highness” is a very dumb movie, unable to combine its penchant for dick jokes with anything resembling intelligence. McBride and co-writer Ben Best consistently opt for the most offensive material they can, confusing crassness with edginess. There are a selection of amusing moments (most of which popped up in the film’s admittedly excellent trailer), but generally it’s all severed Minotaur cocks and references to “the Fuckening”. It’s unimpressive to say the least.

Some of the creature effects have a nice old school vibe about them, and the film’s action is competently choreographed. Tonally “Your Highness” is a bizarre amalgamation of potty mouthed shenanigans and unadorned adventuring, at times it does appear Green thinks he’s making a genuine entry into the fantasy genre. This uneven mix of parody and sincerity hinders the final product, and also explains some of the disappointing lulls in laughter. Granted little of what’s evidenced here is funny in the first place, yet had the filmmakers stuck tighter to a mood of mockery then “Your Highness” might have offered a more gut-busting viewing experience. Of course the sheer complacency of the central story defeats any chances of “Your Highness” earning credibility amongst the rabid fanboy population, it’s simply too lazy to inspire any degree of enthusiasm.

Leaving aside a sleepy Zooey Deschanel, the supporting cast is fine, with James Franco and Justin Theroux emerging as the most successful contributors. Franco plays it straight and engages comfortably with McBride, whilst Theroux manages to turn the film’s villain into a whiny and socially awkward teenager. A little more invention like this and “Your Highness” might actually have been worthwhile. Portman’s line delivery is rusty in chunks, but the recent Oscar winner at least appears onside with the film’s unstoppably silly content. She’s defenseless against the abysmal script, but at least looks game for fun.

“Your Highness” will definitely go down as one of the more underwhelming films of 2011, it’s a first rate education in how to approach production design, but also a firm warning on how not to pen a farce. The jokes are stale, leaving me to wonder why so many talented folks bothered attaching themselves to the project. This is one quest to the multiplex you needn’t bother making.